阅读说明：本技术 基于dp-bpsk的双频段相位编码信号产生的方法及系统 (DP-BPSK-based method and system for generating dual-band phase encoding signal ) 是由 杨淑娜 怀宇继 池灏 杨波 李齐良 曾然 欧军 于 2021-07-29 设计创作，主要内容包括：本发明公开了一种基于DP-BPSK的双频段相位编码信号产生的方法及系统。系统包括LD光源、DP-BPSK调制器、码型信号发生器、第一射频信号发生器、第二射频信号发生器、光电探测器；DP-BPSK调制器包括第一DD-MZM、第二DD-MZM、90°偏振旋转器、偏振合束器；LD光源通过光纤与第一DD-MZM、第二DD-MZM相连；第一DD-MZM与偏振合束器相连,第二DD-MZM通过90°偏振旋转器与偏振合束器相连,偏振合束器与光电探测器相连；码型信号发生器产生的两路信号分别与第一DD-MZM的一个射频口、第二DD-MZM的一个射频口相连；第一射频信号发生器与第一DD-MZM的另一个射频口相连,第二射频信号发生器与第二DD-MZM的另一个射频口相连。本发明利用DP-BPSK调制器,通过将频率不同的射频信号在光域上进行相位编码,生成双频段相位编码信号。(The invention discloses a method and a system for generating a dual-band phase coding signal based on DP-BPSK. The system comprises an LD light source, a DP-BPSK modulator, a code pattern signal generator, a first radio frequency signal generator, a second radio frequency signal generator and a photoelectric detector; the DP-BPSK modulator comprises a first DD-MZM, a second DD-MZM, a 90-degree polarization rotator and a polarization beam combiner; the LD light source is connected with the first DD-MZM and the second DD-MZM through optical fibers; the first DD-MZM is connected with the polarization beam combiner, the second DD-MZM is connected with the polarization beam combiner through the 90-degree polarization rotator, and the polarization beam combiner is connected with the photoelectric detector; two paths of signals generated by the code pattern signal generator are respectively connected with one radio frequency port of the first DD-MZM and one radio frequency port of the second DD-MZM; the first radio frequency signal generator is connected to the other radio frequency port of the first DD-MZM, and the second radio frequency signal generator is connected to the other radio frequency port of the second DD-MZM. The invention utilizes a DP-BPSK modulator to perform phase coding on radio frequency signals with different frequencies in an optical domain to generate a dual-band phase coding signal.)

1. The system for generating the dual-band phase coding signal based on the DP-BPSK is characterized by comprising an LD light source (1), a DP-BPSK modulator, a code pattern signal generator (6), a first radio frequency signal generator (7), a second radio frequency signal generator (8) and a photoelectric detector (9); the DP-BPSK modulator comprises a first DD-MZM (2), a second DD-MZM (3), a 90-degree polarization rotator (4) and a polarization beam combiner (5); the LD light source (1) is connected with the first DD-MZM (2) and the second DD-MZM (3) through optical fibers; the first DD-MZM (2) is connected with a polarization beam combiner (5), the second DD-MZM (3) is connected with the polarization beam combiner (5) through a 90-degree polarization rotator (4), and the polarization beam combiner (5) is connected with a photoelectric detector (9); two paths of signals generated by the code pattern signal generator (6) are respectively connected with one radio frequency port of the first DD-MZM (2) and one radio frequency port of the second DD-MZM (3); a first RF signal generator (7) is connected to the other RF port of the first DD-MZM (2), and a second RF signal generator (8) is connected to the other RF port of the second DD-MZM (3).

2. The DP-BPSK based dual band phase encoded signal generation system of claim 1, wherein the LD light source emits light waves represented as: e_in(t)＝E₀exp(jω_ct) in which E₀Expressed as the electric field amplitude, ω, of the input optical carrier_cIs the center frequency of the input optical carrier.

3. The system for DP-BPSK based dual band phase encoded signal generation of claim 1, wherein the DP-BPSK modulator is an integrated modulator having four rf ports, two dc offsets, and two paths in orthogonal polarization states.

4. The system of claim 1, wherein the first RF signal generator generates a signal of cos (2 π f) as a dual band phase encoded signal₁t) wherein f₁Is the frequency of the radio frequency signal.

5. The system for DP-BPSK based dual-band phase-encoded signal generation as claimed in claim 1 or 4, wherein the RF signal generated by the second RF signal generator is cos (2 π f)₂t) wherein f₂Is the frequency of the radio frequency signal.

6. The system of claim 1, wherein the pattern generator generates two parallel digital signals having a uniform rate of f₁/6。

7. The system for DP-BPSK based dual band phase encoded signal generation of claim 1, wherein the modulated output optical signal is converted to an electrical signal after passing through a photodetector.

8. The DP-BPSK based dual-band phase encoded signal generation system as claimed in claim 1 or 3, wherein the DC bias of the first DD-MZM and the DC bias of the second DD-MZM inside the DP-BPSK modulator are both biased at the maximum transmission point, i.e. V_DC1＝V_DC2＝0。

9. A method for dual band phase encoded signal generation for a system according to any of claims 1-8, comprising the steps of:

s1, the LD light source (1) generates continuous light waves, and the continuous light waves enter a DP-BPSK modulator through optical fibers;

s2, loading the radio frequency signal generated by the first radio frequency signal generator (7) on a first DD-MZM (2) in the DP-BPSK modulator;

s3, loading the radio frequency signal generated by the second radio frequency signal generator (8) on a second DD-MZM (3) in the DP-BPSK modulator;

s4, a code pattern signal generator (6) generates two paths of digital signals as input voltage signals to be loaded on a first DD-MZM (2) and a second DD-MZM (3) of the DP-BPSK modulator respectively;

and S5, inputting the output modulation signal into a photoelectric detector (9) through a polarization beam combiner (5) in the DP-BPSK modulator.

Technical Field

The invention belongs to the technical field of optical communication signal generation, and particularly relates to a dual-band phase-shift keying (DP-BPSK) based method and system for generating a dual-band phase coding signal.

Background

In order to improve the range resolution and velocity resolution of radar, pulse compression technology is widely used in radar systems. The generation of phase encoded signals has been widely studied as an important microwave waveform for pulse compression. Conventionally, the phase encoded signal is generated in the electrical domain using a Direct Digital Synthesizer (DDS). However, with the development of radar technology, it is difficult to meet the requirements of radar for high frequency, large bandwidth, and large frequency tunable range using conventional methods. In order to solve these problems, technicians turn their eyes to the optical domain, and utilize the advantages of the optical domain, such as large frequency operation range, low transmission loss, no electromagnetic interference, small system size, and light weight, to perform signal generation, processing, and transmission operations that cannot be achieved in the electrical domain.

In recent years, schemes for photonically generating phase encoded microwave signals have been proposed. The earliest was achieved by spectral shaping, which was achieved by a programmable Spatial Light Modulator (SLM), and frequency-time mapping, a key advantage of this scheme was its high reconfigurability, which enables reconfigurable waveform generation. However, free space optics based systems are typically lossy and bulky. The second method for generating the photon phase-coded microwave signal is realized by controlling the phase difference between two coherent optical carriers and then performing frequency heterodyne at the PD, and a representative scheme provides a method for generating a high-frequency phase-coded radio-frequency pulse by using an all-fiber element for teaching task at the cell level of university of zhejiang, 2007. A third method for generating a photonic phase-encoded microwave signal is based on the principle of vector sum, and the generation of the phase-encoded signal is realized by the superposition of two vectors, which is typically represented by a photonic microwave phase-encoded pulse generator proposed by Lei M et al, and by properly setting a data sequence applied to a special bias PDM-MZM, binary and quaternary phase-encoded microwave pulses that are not affected by background signals can be generated.

With the continuous improvement of the requirements for radar functions, a concept of a multiband radar is proposed, and different wavebands can complete different tasks under the condition of sharing part of hardware platforms, so that the generation of multiband phase coding signals is a research hotspot in recent years. For example: zhu D et al in 2016 proposed photonic multi-frequency phase-encoded microwave signal generation based on polarization modulation and balanced detection; wu D et al, 2017, propose a photonic scheme for generating a multi-frequency phase-encoded microwave signal based on a dual-output Mach-Zehnder modulator and a balance detection technique. In experimental demonstrations, a multi-band signal having only two frequencies was demonstrated. Furthermore, the use of a multi-wavelength laser source increases the cost of the system and it is difficult to control the power of each frequency component separately unless the power of each individual wavelength of the multi-wavelength laser source can be controlled separately.

Disclosure of Invention

In view of the above situation, the present invention provides a method and a system for generating a dual-band phase encoded signal based on DP-BPSK by using a DP-BPSK modulator to perform phase encoding on radio frequency signals with different frequencies in an optical domain to generate a dual-band phase encoded signal.

In order to achieve the purpose, the invention adopts the following technical scheme:

the system for generating the dual-band phase coding signal based on the DP-BPSK comprises an LD light source, a DP-BPSK modulator, a code pattern signal generator, a first radio frequency signal generator, a second radio frequency signal generator and a photoelectric detector; the DP-BPSK modulator comprises a first DD-MZM, a second DD-MZM, a 90-degree polarization rotator and a polarization beam combiner; the LD light source is connected with the first DD-MZM and the second DD-MZM through optical fibers; the first DD-MZM is connected with the polarization beam combiner, the second DD-MZM is connected with the polarization beam combiner through the 90-degree polarization rotator, and the polarization beam combiner is connected with the photoelectric detector; two paths of signals generated by the code pattern signal generator are respectively connected with one radio frequency port of the first DD-MZM and one radio frequency port of the second DD-MZM; the first radio frequency signal generator is connected to the other radio frequency port of the first DD-MZM, and the second radio frequency signal generator is connected to the other radio frequency port of the second DD-MZM.

The system has simple structure, realizes the generation of the dual-band phase coding signal by only one integrated modulator, and breaks through the limitation of single frequency band; in addition, the phase of the dual-band phase coding signal generated by the invention is only related to the polarity of the digital signal generated by the code pattern generator, and no requirement is made on the power of the digital signal and the radio frequency signal, so that an amplifier is not needed in the whole system. In addition, the invention does not relate to wavelength-dependent devices such as a filter and the like, so that the frequency tunable range of the system is improved.

Further, the light source is an LD light source, and the light wave emitted by the semiconductor laser is represented as: e_in(t)＝E₀ exp(jω_ct) in which E₀Expressed as the electric field amplitude, ω, of the input optical carrier_cIs the center frequency of the input optical carrier.

Furthermore, the DP-BPSK is an integrated modulator, the interior of the DP-BPSK is composed of a DD-MZM, a 90-degree polarization rotator and a polarization beam combiner, the total number of the DD-MZM, the total number of the 90-degree polarization rotator and the total number of the polarization beam combiner are four, two direct current biases are provided, and the upper path and the lower path are respectively in different polarization states.

Further, the first RF signal generator generates the first RF signal as cos (2 π f)₁t) wherein f₁Is the frequency of the radio frequency signal. The invention has no special requirement on the amplitude of the radio frequency signal. Thus, the radio frequency signal does not need to be amplified.

Further, the second RF signal generator generates the second RF signal as cos (2 π f)₂t) wherein f₂No amplification is required for the frequency of the radio frequency signal as well.

Further, the code pattern signal generator generates two paths of digital signals, wherein,the rates of the two paths of digital signals are consistent and are both f₁/6. Since the phase change of the phase encoded signal of the present invention is only related to the polarity of the digital signal. Therefore, the digital signal does not need to be amplified.

Further, after the modulated signal passes through the photodetector, the optical signal is converted into an electrical signal.

Further, two DD-MZM direct current biases in DP-BPSK are both biased at the maximum transmission point, namely V_DC1＝V_DC2＝0。

The invention also discloses a method for generating the dual-band phase coding signal of the system, which comprises the following steps:

s1, the LD light source generates continuous light waves, and the continuous light waves enter the DP-BPSK modulator through an optical fiber;

s2, loading the radio-frequency signal generated by the first radio-frequency signal generator on a first DD-MZM inside the DP-BPSK modulator;

s3, loading the radio-frequency signal generated by the second radio-frequency signal generator on a second DD-MZM inside the DP-BPSK modulator;

s4, generating two paths of digital signals as input voltage signals by a code pattern signal generator and loading the two paths of digital signals on a first DD-MZM and a second DD-MZM of the DP-BPSK modulator respectively;

and S5, inputting the output modulation signal into a photoelectric detector through a polarization beam combiner inside the DP-BPSK modulator.

Compared with the technical scheme of the existing phase coding signal generation, the method and the system based on the DP-BPSK dual-band phase coding signal generation have the advantages that the system structure is simple, the generation of the dual-band phase coding signal is met, wavelength-related devices are not arranged in the whole system, the frequency tunable range is large, and the generation of the phase coding signal is only related to the polarity of a digital signal and is unrelated to the amplitude. Therefore, amplification is not needed in the whole system, the whole system is simplified, and the generated dual-band phase coding signal has potential application value in a multi-band radar system.

Drawings

Fig. 1 is a schematic diagram of a system architecture for DP-BPSK based dual band phase encoded signal generation;

fig. 2 is a graph one of simulation results of the generation of a dual-band phase-encoded pulse signal based on DP-BPSK.

Fig. 3 is a graph two of simulation results generated by a dual-band phase-encoded pulse signal based on DP-BPSK.

1, an LD light source; DD-MZM (Dual drive Mach-Zehnder modulator); DD-MZM (Dual drive Mach-Zehnder modulator); a 4.90 ° polarization rotator; 5. a polarization beam combiner; 2. 3, 4 and 5 together form a DP-BPSK modulator; 6. a code pattern signal generator; 7. a radio frequency signal generator; 8. a radio frequency signal generator; 9. a photodetector.

Detailed Description

The embodiments of the present invention are described below with reference to specific embodiments, and other advantages and effects of the present invention will be easily understood by those skilled in the art from the disclosure of the present specification. The invention is capable of other and different embodiments and of being practiced or of being carried out in various ways, and its several details are capable of modification in various respects, all without departing from the spirit and scope of the present invention. It is to be noted that the features in the following embodiments and examples may be combined with each other without conflict.

According to the existing phase encoding signal generation technology, the invention utilizes a DP-BPSK modulator to complete the generation of the dual-band phase encoding signal through two paths of DD-MZMs with different polarization states integrated inside.

Example 1

As shown in fig. 1, the system for generating a dual-band phase-encoded signal based on DP-BPSK of this embodiment includes: the device comprises an LD light source 1, a DD-MZM2, a DD-MZM3, a 90-degree polarization rotator 4, a polarization beam combiner 5, a code pattern signal generator 6, a radio frequency signal generator 7, a radio frequency signal generator 8 and a photoelectric detector 9. The DD-MZM2, the DD-MZM3, the 90-degree polarization rotator 4 and the polarization beam combiner 5 jointly form a DP-BPSK modulator.

The LD light source 1 is connected with the DD-MZM2 and the DD-MZM3 of the DP-BPSK modulator through optical fibers; the DD-MZM2 is connected to the polarization beam combiner 5, the DD-MZM3 is connected to the polarization beam combiner 5 through the 90 ° polarization rotator 4, the polarization beam combiner 5 is connected to the photodetector 9, and the modulated signal is transmitted to the photodetector 9. The DP-BPSK modulator is internally divided into two paths of DD-MZMs with different polarization states, and two paths of signals generated by the code pattern signal generator 6 are respectively connected with one radio frequency port of the two paths of DD-MZMs; two radio frequency signal generators 7 and 8 are respectively connected with the other radio frequency port of the two paths of DD-MZM.

Example 2

The embodiment is based on a method for generating a dual-band phase encoded signal of the system of embodiment 1, and the method comprises the following specific steps:

in step S1, the continuous wave light source generated by the semiconductor Laser (LD)1 emits light waves represented by: e_in(t)＝E₀exp(jω_ct) in which E₀Expressed as the electric field amplitude, ω, of the input optical carrier_cIs the center frequency of the input optical carrier;

step S2, the rf signal generated by the first rf signal generator 7 is loaded on the first DD-MZM2 inside the DP-BPSK modulator;

step S3, the rf signal generated by the second rf signal generator 8 is loaded on the second DD-MZM3 inside the DP-BPSK modulator;

step S4, the code pattern signal generator 6 generates two paths of digital signals as input voltage signals to be loaded on a first DD-MZM2 and a second DD-MZM3 of the DP-BPSK modulator respectively;

in step S5, the output modulation signal is input to the photodetector 9 through the polarization beam combiner 5 inside the DP-BPSK modulator.

Steps S2 to S5 show the input and output processes of the modulator, and the specific theoretical derivation is as follows:

wherein, ω is_cFor the center frequency, omega, of the light carrier output by the LD₁And ω₂Frequency, beta, of the radio-frequency signals respectively generated by the two radio-frequency signal sources₁And beta₂Modulation depth beta for radio frequency signals₁＝πV₁/V_π，β₂＝πV₂/V_π

V₁、V₂For the amplitude of the input radio-frequency signal, phi₁、φ₂For phase induced by DC offset, gamma₁、γ₂For the modulation depth, s, of the input digital signal₁(t)、s₂And (t) is an input digital signal.

Expanding the expression by using a Bessel function to obtain:

wherein, J_nRepresenting the expansion coefficient of the bessel function, the high-order sidebands are negligible due to the small-signal modulation.

Let phi₁＝φ₂The modulated signal, after PD, can be represented as:

i₁＝E_x*E_x ^*αJ₁(β)cos(ω₁t)sin(γ₁s₁(t))+J₀(β)cos(γ₁s₁(t))

i₂＝E_y*E_y ^*αJ₁(β)cos(ω₂t)sin(γ₂s₂(t))+J₀(β)cos(γ₂s₂(t))

when s is₁(t)＝{1,-1}，s₂The (t) {1, -1} time results in a two-band phase encoded signal after PD.

Fig. 2 shows a simulated 3GHz phase encoded signal and fig. 3 shows a simulated 6GHz phase encoded signal.

Compared with the technical scheme of the existing phase coding signal generation, the method and the system for generating the dual-band phase coding signal based on the DP-BPSK have the advantages that the system structure is simple, the generation of dual bands is simultaneously met, wavelength-related devices are not arranged in the whole system, the frequency tunable range is large, the phase coding signal is only related to the polarity of a digital signal and is not related to the amplitude, the amplification is not needed in the whole system, the whole system is simplified, and the generated dual-band phase coding signal has potential application value in a multi-band radar system.

The foregoing is considered as illustrative of the preferred embodiments of the invention and the technical principles employed. It will be understood by those skilled in the art that the present invention is not limited to the particular embodiments described herein, but is capable of various obvious changes, rearrangements and substitutions as will now become apparent to those skilled in the art without departing from the scope of the invention. Therefore, although the present invention has been described in greater detail by the above embodiments, the present invention is not limited to the above embodiments, and may include other equivalent embodiments without departing from the spirit of the present invention, and the scope of the present invention is determined by the scope of the appended claims.